Landscape-scale effects of Christmas-tree plantations in an intensively used low-mountain landscape – Applying breeding bird assemblages as indicators

Abstract

Novel ecosystems are characterised by recent establishment due to human activities and new species combinations. A characteristic example in farmlands are Christmas-tree plantations. The aim of this study is to evaluate the landscape-scale effects of the novel ecosystem Christmas-tree plantation on breeding bird assemblages in an important European stronghold of Christmas-tree production, the intensively used low-mountain landscape of the Hochsauerland (Central Europe), in comparison with currently competing land-use types.The study revealed that the five studied landscape types differed in habitat composition and landscape diversity. Landscape diversity was significantly highest in the two types of Christmas-tree plantation landscapes and windthrow landscapes, differing from grassland and forest landscapes. Bird species assemblages clearly responded to the differences in habitat composition. This was especially true for threatened species having a peak of species richness and breeding-pair density in the two types of Christmas-tree plantation landscapes and slightly weakened at windthrow landscapes.The high species richness of threatened breeding bird species in Christmas-tree plantation landscapes was driven mainly by high landscape heterogeneity. Densities of the threatened indicator species of the Christmas-tree plantation landscapes were probably promoted by (i) high availability of suitable food (arthropods, seeds) and (ii) high accessibility to the food resources due to bare ground (tree pipit [Anthus trivialis], woodlark [Lullula arborea]) or low-growing vegetation (linnet [Carduelis cannabina], yellowhammer [Emberiza citronella]) in the Christmas-tree plantations. For the woodlark, Christmas-tree plantations are even among the most important strongholds in the German Federal State of North Rhine-Westphalia.